1. Field of the Invention
The invention relates to a Liquid dispenser, in particular dosing dispenser, comprising a supplying device with a supplying or dosing cylinder, a supplying or dosing plunger movable therein for supplying liquid from a container to an outlet duct, for the delivery of the liquid via an outlet port of the outlet duct, wherein the outlet duct and a return duct extending there along are formed in a discharge tubule. Further, the invention relates to a discharge tubule kit system therefore and a discharge tubule, in particular for this type of liquid dispenser.
2. Background Art
From DE 41 37 351 C2 a liquid dispenser is known which comprises a valve block with a three-way valve, via which alternatively an amount of liquid supplied by a dosing cylinder from a container is either fed into an outlet duct arranged in a discharge tubule, or, essentially without passing through the discharge tubule, can be passed back directly into the container.
With this type of design it has however been found to be a disadvantage in that even when the valve is brought into the return position after an outlet process, a relevant amount of liquid always remains in the discharge tubule, which cannot be rinsed out and can therefore dry up or drip out. Moreover, the dosing accuracy at the start of a dosing process is problematical due to the large dead volume.
The first time this device is put into operation the amount of liquid to be dosed cannot be exactly measured, because the dead volume of the still unfilled outlet duct cannot be taken into consideration precisely. In order to obtain exact dosed amounts it is therefore necessary to fill the discharge tubule with liquid before the first time it is used, which however again gives the risk of an undesired outlet of liquid.
From DE 198 07 647 C2 a liquid dispenser of the type mentioned at the beginning is known, which comprises a common outlet duct and a return duct on one discharge tubule with an alternative connection of the return duct to the outlet duct, so that also a flushing mode is possible as well as liquid dispensing.